Investigators trying to determine what caused last week’s deadly midair collision between a US military Black Hawk helicopter and an American Airlines plane near Washington, DC, briefed lawmakers Thursday on what they’ve learned after combing through data from both aircraft and air traffic control.

The training of U.S. military helicopter pilots is getting heightened attention following the mid-air collision between an Army Black Hawk helicopter and a passenger jet.

Readings have been compared from the black box recovered from American Eagle flight 5342 and the air traffic control tower about the Black Hawk helicopter